Conventionally, drilling holes in stone, concrete, etc. is done by attaching a drill bit made of cemented carbide or the like to a vibrating drilling device and by applying both rotation and vibration (strike) in an axial direction to the drill bit.
One example of the drill bit of this type is constructed such that a plurality of cutting blades are arranged in a circumferential direction of the drill bit, a connecting ridge line between a cutting face and a flank which are formed in each cutting blade acts as a cutting edge, and radially inner ends of the cutting edges are coupled to each other at a center portion of a bit tip end (see Patent Document 1).
Patent Document 1: Japanese Laid-Open Patent Application Publication No. 2002-178328